Autism spectrum disorder (ASD) affects an estimated 1% of children in the United States and yet many fundamental questions about the biology of ASD, potential risk factors, effective treatments and interventions, and impacts throughout life remain unanswered. Important advances have been made in understanding the complexity of ASD, but additional work is needed to fully understand how biological and external environmental factors contribute to ASD, identify the most effective interventions and services, and improve the quality of life for people with ASD and their families. The Interagency Autism Coordinating Committee (IACC) Strategic Plan for ASD Research was created with the intent to accelerate and inspire research that will profoundly improve the health and well-being of every person on the autism spectrum across the lifespan. The Plan provides a blueprint for autism research that is advisory to the Department of Health and Human Services and serves as a basis for partnerships with other agencies and private organizations involved in autism research and services. Under the Combating Autism Act of 2006, it must be updated on an annual basis. To this end, the 2011 Plan has been updated by the IACC to reflect important new scientific advances in the field over the past year, emerging areas of opportunity, and areas where more research is necessary. Input from the ASD community, advocacy groups, research funding organizations, and the scientific community has continued to be a critical aspect of the updating process. The 2011 Plan includes an additional 16 objectives and newly developed addendum sections for each chapter describing what has recently been learned, what gap areas have emerged, and what progress is being made in fulfilling the objectives. [For "2010 Strategic Plan for Autism Spectrum Disorder Research," see ED524616.]